Dear All,
i am new here, looking for some help since i am trying to repair the instrument in the subject. I honestly say that i get it from a kind of "bid" for few money and trying the repair. So i don't have much information on the origin of the fault.
Anyway,
ISSUE: at power on, an internal relay (on the input measurement part "clicks"), then nothing is displayed out in the front LCD.
What i did until now:
1) measured that all the main PS voltages are there, there are 2 7805, 1 7809, 1 LM399. Output voltages are all there except for 7809 where i measure 11.2.
here a picture
http://i222.photobucket.com/albums/dd237/Zadpics/Tektronix DMM4020 Bench Multimeter/DMM4020-PCB-Annotated.jpg
2) i briefly checked the cpu, clock is correct (4 Mhz), cpu is correctly powered 3,3V
3) i moved so the the LCD board, there is a small PS to generate 40V (called high voltages)
http://i222.photobucket.com/albums/dd237/Zadpics/Tektronix DMM4020 Bench Multimeter/Fluke-Front-Panel.jpg
On VH i measured initially 40V , but now, after some measurements here and there, i read 24V, (hope i didn't damaged anything additional).
On 9V i measure 11.2
On 5V i measure 5
On EK 3V.
Some questions:
Is there a way that i can try LCD segments separately, so to be sure LCD is working ?
I don't have any service manual also.
Any help on how to proceed is welcome.
Many thanks,
Regards,
Angelo
i am new here, looking for some help since i am trying to repair the instrument in the subject. I honestly say that i get it from a kind of "bid" for few money and trying the repair. So i don't have much information on the origin of the fault.
Anyway,
ISSUE: at power on, an internal relay (on the input measurement part "clicks"), then nothing is displayed out in the front LCD.
What i did until now:
1) measured that all the main PS voltages are there, there are 2 7805, 1 7809, 1 LM399. Output voltages are all there except for 7809 where i measure 11.2.
here a picture
http://i222.photobucket.com/albums/dd237/Zadpics/Tektronix DMM4020 Bench Multimeter/DMM4020-PCB-Annotated.jpg
2) i briefly checked the cpu, clock is correct (4 Mhz), cpu is correctly powered 3,3V
3) i moved so the the LCD board, there is a small PS to generate 40V (called high voltages)
http://i222.photobucket.com/albums/dd237/Zadpics/Tektronix DMM4020 Bench Multimeter/Fluke-Front-Panel.jpg
On VH i measured initially 40V , but now, after some measurements here and there, i read 24V, (hope i didn't damaged anything additional).
On 9V i measure 11.2
On 5V i measure 5
On EK 3V.
Some questions:
Is there a way that i can try LCD segments separately, so to be sure LCD is working ?
I don't have any service manual also.
Any help on how to proceed is welcome.
Many thanks,
Regards,
Angelo